Transfer existing installation after acquiring Steam key.

[JackTheSpades]

I followed the steps outlined by the FAQ and profile to get the Steam key for Factorio after I purchased it directly long ago.
Redeeming the key worked fine and I am now presented with the option to "Install" on Steam.

Needless to say I already have to game installed from the previous purchase.
Following the information from the wiki on the Application Directory it seems that Steam would install the game in a different directory.
I don't really mind simply reinstalling the game but do I have to do anything beyond that to "transfer" from my existing installation to the Steam one?
My saves and mods are located in the AppData directory. Would the Steam installation also check there for existing saves?

I simply want to make sure that everything is in working order for the upcoming Space Age extension.

[Bilka]

My saves and mods are located in the AppData directory. Would the Steam installation also check there for existing saves?

Yes, both install methods default to using AppData.